Accidentally unplugged Time Machine backup without ejecting! What now?

Question

Accidentally unplugged Time Machine backup without ejecting! What now?

I accidentally unplugged my Time Machine backup hard drive today without ejecting it first :-/ It had successfully finished making a backup a couple of minutes before this happened and so I hope that this hasn’t corrupted the drive. I checked to see if I could retrieve files from my backups and seem to be able to do that without an issue.

I then ran the “tmutil compare” and “tmutil compare -s” commands via Terminal to verify the backups. To my surprise (and mild horror!) I got the following results: “Added: 80.7K Removed: 47.9M Changed: 199.9M” I expected these to be around 0 as I had run the commands right after running a backup and without making any changes to the files on the Mac. I disabled WiFi for good measure too. The majority of the changes seem to come from one file “! 148.4M (size) /Users/username/Library/Application Support/Google/Drive/user_default/sync_log.log”

Is my drive in good health or should I be concerned? I would greatly appreciate pointers from the excellent community here.

Posted on Jul 12, 2017 6:28 AM

Reply

Answer 1

John Galt

Level 10

155,222 points

Jul 12, 2017 8:08 AM in response to Mac Addict AJ

It is literally impossible to induce corruption on a journaled HFS+ volume (a format Time Machine is required to have) simply by disconnecting it. Time Machine is designed specifically to address that sort of event, since a backup volume can disappear at any moment and for any number of reasons.

Having said that it is never a good idea to depend upon one and only one Time Machine backup drive. Two or more are advantageous. Any drive can fail at any time.

Reply

Answer 2

Jul 12, 2017 8:07 AM in response to Mac Addict AJ

It shouldn't be a problem. If it were in the process of backing up, it should just continue from where it left off when you plug it back in. If backups run normally, it should be a short process as opposed to doing another full backup. Those changes you posted are about normal for little or no change to the next backup.

Reply

Answer 3

Jul 12, 2017 8:22 AM in response to John Galt

Phew, that's good to know! Thank you both for chipping in. What alarmed me was the “Changed: 199.9M” in the “tmutil compare -s” results. I wasn't expecting such a large amount of data to show up as changed in such a short period of time, especially when the Mac was sitting idle and disconnected from the Internet.

It would be nice if Apple were to include a Verify Backups option for local backups too and not just for networked ones.

@John Galt - I have a second SuperDuper backup and also backup important files to the cloud but count on Time Machine first when I need help retrieving something.

Reply

Answer 4

John Galt

Level 10

155,222 points

Jul 12, 2017 9:51 AM in response to Mac Addict AJ

It would be nice if Apple were to include a Verify Backups option for local backups too and not just for networked ones.

Hold a Shift key while selecting the Time Machine icon in your Mac's menu bar, and select "Back Up With Consistency Scan".

Reply

Answer 5

Jul 12, 2017 12:05 PM in response to John Galt

Thanks again! That is very interesting. All the more so as there is very little information to be found about it. Does it give you a summary of findings once it's done?

Would you recommend turning off Time Machine, going to Disk Utility and putting the Time Machine disk through First Aid?

Reply

Answer 6

Bookbee

Level 1

4 points

Jul 12, 2017 2:46 PM in response to Mac Addict AJ

The Mac 🙂 is pretty great at handling ejection problems. I have experience "a forget to eject" once or twice, myself, when in a hurry. No problems. just plug it back in and choose your device, if needed, in time machine and back up again. It doesn't hurt the Mac or your XHD (if you have a decent one). Also, I agree with having a 2nd back up device. I use a 4T for Mac; it's pocket size and works great as my 2nd back up.

Reply

Answer 7

John Galt

Level 10

155,222 points

Jul 12, 2017 3:02 PM in response to Mac Addict AJ

Does it give you a summary of findings once it's done?

Nope. TM will only inform you of a failure to back up with an ⚠ icon. Clicking that will describe the reason, though it tends to be vague. Specific reasons might be revealed by extracting relevant information from system.log.

Would you recommend turning off Time Machine, going to Disk Utility and putting the Time Machine disk through First Aid?

You can do that if you wish, but Disk Utility's "... appears to be OK" conclusions don't exactly instill confidence, and are therefore of little value. It's not necessary to turn off Time Machine first. If problems are identified and corrected by Disk Utility (or any other utility for that matter), the "repair" will only be temporary, and should be considered a warning that the drive should no longer be relied upon.

When a backup drive fails, TM will write-protect the previous backup and tell you to run Disk Utility. See the above for what I think of that. It's yet another reason to maintain more than one TM backup drive. If one becomes unreliable, throw it away. They're inexpensive enough, if you shop around.

Reply

Answer 8

Jul 13, 2017 2:55 AM in response to Mac Addict AJ

I ran First Aid via Disk Utility and got the following results. Are the highlighted portions ("Growing Logical Volume" and "Growing file system") to be expected? Does the report look ok?

Verifying storage system

Checking volume

disk2s2: Scan for Volume Headers

disk2s2: Scan for Disk Labels

Logical Volume Group 29A05C1A-AA2B-470A-A3D3-6CCA3DE9A8CB on 1 device

disk2s2: Scan for Metadata Volume

Logical Volume Group has a 24 MB Metadata Volume with double redundancy

Start scanning metadata for a valid checkpoint

Load and verify Segment Headers

Load and verify Checkpoint Payload

Load and verify Transaction Segment

Incorporate 0 newer non-checkpoint transactions

Load and verify Virtual Address Table

Load and verify Segment Usage Table

Load and verify Metadata Superblock

Load and verify Logical Volumes B-Trees

Logical Volume Group contains 1 Logical Volume

Load and verify D62B417C-E970-4A42-8572-97C52AD6B7B1

Load and verify E5633850-2EA0-447D-89E8-09B473769BD8

Load and verify Freespace Summary

Load and verify Block Accounting

Load and verify Live Virtual Addresses

Newest transaction commit checkpoint is valid

Load and verify Segment Cleaning

The volume 29A05C1A-AA2B-470A-A3D3-6CCA3DE9A8CB appears to be OK

Storage system check exit code is 0.

Repairing file system.

Checking Journaled HFS Plus volume.

Checking extents overflow file.

Checking catalog file.

Checking multi-linked files.

Checking catalog hierarchy.

Checking extended attributes file.

Checking multi-linked directories.

Checking volume bitmap.

Checking volume information.

Trimming unused blocks.

The volume Time Machine (MBP) appears to be OK.

File system check exit code is 0.

Updating boot support partitions for the volume as required.

Checking for overcommitted space in Logical Volume Group

Fixing size of logical volume to fill logical volume group.

Verifying file system.

Checking Journaled HFS Plus volume.

Checking extents overflow file.

Checking catalog file.

Checking multi-linked files.

Checking catalog hierarchy.

Checking extended attributes file.

Checking multi-linked directories.

Checking volume bitmap.

Checking volume information.

The volume Time Machine (MBP) appears to be OK.

File system check exit code is 0.

Growing Logical Volume

Resizing Core Storage Logical Volume structures

Resized Core Storage Logical Volume to 14,99,59,78,97,728 bytes

Growing file system

Operation successful.

Reply

Answer 9

John Galt

Level 10

155,222 points

Jul 13, 2017 6:42 AM in response to Mac Addict AJ

Mac Addict AJ wrote:

I ran First Aid via Disk Utility and got the following results. Are the highlighted portions ("Growing Logical Volume" and "Growing file system") to be expected? Does the report look ok?

Yes to both questions.

Reply